The Verge posted a look at The Nightmare Cooperative as an intro to the usually uncompromisingly sadistic roguelike genre:
At the outset, you control a single explorer, moving one square at a time through a series of rooms. The turn-based structure means that speed isn’t important, but every time you make a move your enemies will do the same, forcing you to plan ahead accordingly. Where things get especially tricky is that your party will grow as you meet other explorers along the way — and you’ll control the entire group at the same time.
This is the first I’ve heard of it, and it looks neat: